PURPOSE: To search for CT findings which helpfully differentiate mucinous from nonmucinousbronchi-oloalveolar carcinoma and to assess the difference in stages between the two types of tumors. Twenty-two patients with pathologically proven bronchioloalveolar carcinoma (BAC) were included inthis study. On the basis of CT findings, tumors were classified as either solitary or multiple and as eithermass/nodule, consolidation, or mixed type. CT stages of the tumors were determined by two radiologists andconclusions were reached by consensus. RESULTS: Twelve patients had nonmucinous BACs and ten had mucinous BACs.Among the ten cases of mucinous BAC, six were solitary and four were multiple. These were mass/nodule (n=3),consolidation (n=5), and mixed pattern (n=2). In contrast, among the twelve cases of nonmucinous BAC, six weresolitary and six were multiple. All were mass/nodule, except for one mixed type. Among the mucinous BACs, threewere operable and seven (above stage IIIa) were inoperable. Among the nonmucinous BACs, four were operable andeight were inoperable. CONCLUSION: Consolidation was more common in mucinous BAC and mass/nodule was more commonin non-mucinous BAC (p<0.05). There was no difference in tumor stages between mucinous and nonmucinous types ofBAC (p>0.05).